Preparation method and application of thiocalix[4]arene tetrasulfonate eluent

Abstract

A preparation method and application of a thiocalix[4]arene tetrasulfonate eluent, which belongs to the field of soil leaching. The present invention aims to solve the problem that existing soil eluents cannot achieve the simultaneous removal of pollutants in soil contaminated by heavy metals and polycyclic aromatic hydrocarbons. Method: 1. Preparation of thiocalixarene; 2. Preparation of thiosulfonated calixarene. Application: It is used as an eluent to simultaneously remove heavy metals and polycyclic aromatic hydrocarbons in soil. The present invention is used for the preparation method and application of a thiocalix[4]arene tetrasulfonate eluent.

Description

Technical Field

[0001] The invention belongs to the field of soil washing. Background Art

[0002] The long-term nature of heavy metal-PAH contamination and complex occurrence patterns at steel and coking complexes in Northeast China make coordinated soil remediation challenging. Traditional methods for removing heavy metal-PAH contaminated soil, such as phytoremediation, microbial remediation, the use of oxidants, and heat treatment, all have significant drawbacks, including time-consuming and demanding conditions (phytoremediation and microbial remediation), soil fertility damage (oxidation and heat treatment), and high costs (heat treatment). Soil leaching agents, as an efficient, low-cost, and environmentally friendly soil remediation technology, can overcome these limitations. Traditional soil leaching agents, such as organic acids, chelating agents, and surfactants, can only treat single contaminated soils and are incapable of removing contaminants from soils contaminated with both heavy metals and PAHs. Furthermore, surfactants, which remove PAHs, alter the physical and chemical properties of the soil, reducing nutrients like humus, significantly reducing soil fertility and depleting soil functionality. Surfactants also fail to simultaneously remove heavy metals. Summary of the Invention

[0003] The present invention aims to solve the problem that existing soil leaching agents cannot achieve the simultaneous removal of pollutants in soil contaminated by heavy metals and polycyclic aromatic hydrocarbons, and further provides a preparation method and application of a thiocalix[4]arene tetrasulfonate leaching agent.

[0004] A method for preparing a thiocalix[4]arene tetrasulfonate eluent is carried out according to the following steps:

[0005] 1. Preparation of Thiacalixarene:

[0006] Under nitrogen protection, a mixture of p-tert-butylphenol, sulfur, and NaOH is stirred and mixed with tetraethylene glycol dimethyl ether to obtain a mixture, and the mixture is maintained at a temperature of 228° C. to 233° C. and nitrogen is introduced for 2.5 hours to 4.5 hours to obtain a dark red product, and the dark red product is cooled to room temperature, diluted with toluene and diethyl ether, and then a sulfuric acid solution is added to obtain a suspension, and the suspension is filtered, and then chloroform is added for recrystallization, and finally dried to obtain thiacalixarene;

[0007] The molar ratio of p-tert-butylphenol to sulfur in the mixture is 1:(1.9-2.1); the molar ratio of p-tert-butylphenol to NaOH in the mixture is 1:(0.45-0.55); the volume ratio of NaOH to tetraethylene glycol dimethyl ether in the mixture is 1 mol:(90-110) mL;

[0008] 2. Preparation of thiosulfonated calixarene:

[0009] Mix thiacalixarene and concentrated sulfuric acid, react for 22h to 28h under stirring at 80℃ to 91℃, and finally cool to obtain a mixed product. The mixed product is placed in ice water, filtered to remove solid residues, and a filtrate is obtained. White particles are repeatedly precipitated in the filtrate to obtain a thiacalix[4]arene tetrasulfonate eluent;

[0010] The mass ratio of the thiacalixarene to the concentrated sulfuric acid is 1g: (9.6-10.8)mL.

[0011] The invention discloses an application of a thiocalix[4]arene tetrasulfonate eluent, which can be used as an eluent to simultaneously remove heavy metals and polycyclic aromatic hydrocarbons in soil.

[0012] The beneficial effects of the present invention are:

[0013] 1) With the purpose of simultaneously removing heavy metals and polycyclic aromatic hydrocarbons from soil, the traditional calixarene was constructed to be amphiphilic, and the volume of the hydrophobic cavity structure was modified so that it could specifically bind to heavy metal polycyclic aromatic hydrocarbons and have a certain hydrophilicity. An amphiphilic thiocalix[4]arene tetrasulfonate (TSC4X) was designed. FTIR, NMR, and XRD results showed that the modified structure of the calixarene was consistent with the designed structure.

[0014] 2) The designed amphiphilic thiocalix[4]arene tetrasulfonate was used to remove pollutants in soil contaminated by heavy metals and polycyclic aromatic hydrocarbons; at the same time, the eluent did not significantly reduce the nutrient elements such as potassium ions, calcium ions and soil humus in the soil.

[0015] 3) FTIR, NMR, XRD, and scanning electron microscopy characterization of TSC4X bound to naphthalene, copper, and both naphthalene and copper, and structural optimization of the resulting complexes. Analysis of surface electrostatic changes before and after binding, as well as electron orbital transitions and weak interactions, revealed that TSC4X binds primarily through hydrophobic interactions, van der Waals forces, OH…π bonds, π…π bonds, and electrostatic interactions, with one of the naphthalene benzene rings entering the hydrophobic aromatic cavity of TSC4X. The sulfur and oxygen atoms at the lower edge of TSC4X co-coordinate with the copper, distorting the TSC4X architecture. UV and fluorescence titration experiments with TSC4X in the presence of copper, naphthalene, and copper ions and naphthalene molecules revealed a 1:1 binding stoichiometry, consistent with both experimental characterization and computational chemistry.

[0016] Figures in the specification

[0017] Figure 1This is the NMR spectrum of the thiocalix[4]arene tetrasulfonate eluent prepared in Example 1;

[0018] Figure 2 This is the XRD diffraction spectrum of the thiocalix[4]arene tetrasulfonate eluent prepared in Example 1;

[0019] Figure 3 This is the infrared spectrum of the thiocalix[4]arene tetrasulfonate eluent prepared in Example 1;

[0020] Figure 4 The test of factors affecting the removal of copper, zinc and lead in soil by the thiocalix[4]arene tetrasulfonate eluent prepared in Example 1, a) degradation kinetics, b) the effect of TSC4X concentration, c) the effect of solid-liquid ratio, d) the effect of pH value;

[0021] Figure 5 The test of factors affecting the removal of naphthalene, fluoranthene and pyrene from soil by the thiocalix[4]arene tetrasulfonate eluent prepared in Example 1, a) degradation kinetics, b) the effect of TSC4X concentration, c) the effect of solid-liquid ratio, d) the effect of pH value;

[0022] Figure 6 IR spectra of the thiocalix[4]arene tetrasulfonate eluent, naphthalene, TSC4X-naphthalene complex, TSC4X-copper complex, and TSC4X-naphthalene-copper complex prepared in Example 1;

[0023] Figure 7 XRD diffraction patterns of the thiocalix[4]arene tetrasulfonate eluent, naphthalene, TSC4X-naphthalene complex, TSC4X-copper complex, and TSC4X-naphthalene-copper complex prepared in Example 1;

[0024] Figure 8 The hydrogen NMR spectra of the thiocalix[4]arene tetrasulfonate eluent, naphthalene and TSC4X-naphthalene complex prepared in Example 1;

[0025] Figure 9 Scanning electron micrographs of the thiocalix[4]arene tetrasulfonate eluent and its composite prepared in Example 1: (a) TSC4X scale 200nm, (b) TSC4X scale 2μm, (c) TSC4X-Cu scale 200nm, (d) TSC4X-copper scale 2μm and S, O, and Cu element distribution diagram, (e) TSC4X-naphthalene scale 200nm, (f) TSC4X-naphthalene scale 2μm, (g) TSC4X-copper-naphthalene scale 200nm, (h) TSC4X-copper-naphthalene scale 2μm and S, O, and Cu element distribution diagram;

[0026] Figure 10Titration diagram of the thiocalix[4]arene tetrasulfonate eluent and its complex prepared in Example 1, (a) UV spectra of TSC4X-naphthalene complex solutions with different molar ratios, (b) UV spectra of TSC4X and naphthalene after correction by the inverse ratio method, and the relationship between the maximum absorbance of TSC4X and naphthalene with different molar ratios, (c) UV spectra of TSC4X and copper, (d) UV spectra of TSC4X-Cu 2+ Metrology analysis, (e)TSC4X-naphthalene-Cu 2+ Fluorescence spectra, (f) copper ion concentration and TSC4X-naphthalene-Cu 2+ Maximum fluorescence spectrum relationship of the composite structure;

[0027] Figure 11 Structural optimization diagrams of the thiocalix[4]arene tetrasulfonate eluent and its composite prepared in Example 1, (a), (b) TSC4X top view and front view, (c) naphthalene, (d), (e) TSC4X-naphthalene top view and front view, (f), (g) TSC4X-copper front view and top view, (h) TSC4X-copper-naphthalene;

[0028] Figure 12 Van der Waals surface electrostatic distribution diagram of the thiocalix[4]arene tetrasulfonate eluent and its composite prepared in Example 1, (a) TSC4X, (b) naphthalene, (c, d) top view and front view of TSC4X-naphthalene, (e, f) top view and front view of TSC4X-Cu-naphthalene, (g) front view of TSC4X-Cu;

[0029] Figure 13 The weak interaction between the thiocalix[4]arene tetrasulfonate eluent prepared in Example 1 and naphthalene, a) is the weak interaction between TSC4X and naphthalene, and b) is the scatter plot of the weak interaction;

[0030] Figure 14 The molecular orbital topology of the thiocalix[4]arene tetrasulfonate eluent prepared in Example 1 combined with naphthalene to participate in the electronic transition of the main absorption band;

[0031] Figure 15 The molecular orbital topology of the thiocalix[4]arene tetrasulfonate eluent prepared in Example 1 and copper participating in the electronic transition of the main absorption band;

[0032] Figure 16 Dynamic changes in respiration intensity before and after eluting different soils with the thiocalix[4]arene tetrasulfonate eluent prepared in Example 1: (a) original soil, (b) low-concentration contaminated soil, (c) medium-concentration contaminated soil, and (d) high-concentration contaminated soil. DETAILED DESCRIPTION

[0033] Specific embodiment 1: This embodiment is a method for preparing a thiocalix[4]arene tetrasulfonate eluent, which is carried out according to the following steps:

[0034] 1. Preparation of Thiacalixarene:

[0035] Under nitrogen protection, a mixture of p-tert-butylphenol, sulfur, and NaOH is stirred and mixed with tetraethylene glycol dimethyl ether to obtain a mixture, and the mixture is maintained at a temperature of 228° C. to 233° C. and nitrogen is introduced for 2.5 hours to 4.5 hours to obtain a dark red product, and the dark red product is cooled to room temperature, diluted with toluene and diethyl ether, and then a sulfuric acid solution is added to obtain a suspension, and the suspension is filtered, and then chloroform is added for recrystallization, and finally dried to obtain thiacalixarene;

[0036] The molar ratio of p-tert-butylphenol to sulfur in the mixture is 1:(1.9-2.1); the molar ratio of p-tert-butylphenol to NaOH in the mixture is 1:(0.45-0.55); the volume ratio of NaOH to tetraethylene glycol dimethyl ether in the mixture is 1 mol:(85-100) mL;

[0037] 2. Preparation of thiosulfonated calixarene:

[0038] Mix thiacalixarene and concentrated sulfuric acid, react for 22h to 28h under stirring at 80℃ to 91℃, and finally cool to obtain a mixed product. The mixed product is placed in ice water, filtered to remove solid residues, and a filtrate is obtained. White particles are repeatedly precipitated in the filtrate to obtain a thiacalix[4]arene tetrasulfonate eluent;

[0039] The mass ratio of the thiacalixarene to the concentrated sulfuric acid is 1g: (9.6-10.8)mL.

[0040] This specific embodiment targets the molecular size of PAHs and the characteristics of surface electrostatics and is based on super-hierarchical structure design to enable it to have the ability to specifically adsorb PAHs and heavy metal pollutants.

[0041] The beneficial effects of this embodiment are:

[0042] 1) With the purpose of simultaneously removing heavy metals and polycyclic aromatic hydrocarbons from soil, the traditional calixarene was constructed to be amphiphilic, and the volume of the hydrophobic cavity structure was modified so that it could specifically bind to heavy metal polycyclic aromatic hydrocarbons and have a certain hydrophilicity. An amphiphilic thiocalix[4]arene tetrasulfonate (TSC4X) was designed. FTIR, NMR, and XRD results showed that the modified structure of the calixarene was consistent with the designed structure.

[0043] 2) The designed amphiphilic thiocalix[4]arene tetrasulfonate was used to remove pollutants in soil contaminated by heavy metals and polycyclic aromatic hydrocarbons; at the same time, the eluent did not significantly reduce the nutrient elements such as potassium ions, calcium ions and soil humus in the soil.

[0044] 3) FTIR, NMR, XRD, and scanning electron microscopy characterization of TSC4X bound to naphthalene, copper, and both naphthalene and copper, and structural optimization of the resulting complexes. Analysis of surface electrostatic changes before and after binding, as well as electron orbital transitions and weak interactions, revealed that TSC4X binds primarily through hydrophobic interactions, van der Waals forces, OH…π bonds, π…π bonds, and electrostatic interactions, with one of the naphthalene benzene rings entering the hydrophobic aromatic cavity of TSC4X. The sulfur and oxygen atoms at the lower edge of TSC4X co-coordinate with the copper, distorting the TSC4X architecture. UV and fluorescence titration experiments with TSC4X in the presence of copper, naphthalene, and copper ions and naphthalene molecules revealed a 1:1 binding stoichiometry, consistent with both experimental characterization and computational chemistry.

[0045] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that in step 1, nitrogen is introduced at a rate of 0.23 g / s to 0.27 g / s to remove the generated by-product hydrogen sulfide. Other aspects are the same as specific embodiment 1.

[0046] Specific embodiment 3: This embodiment differs from specific embodiment 1 or 2 in that in step 1, the mixture is heated to 228°C to 233°C at a heating rate of 37°C / min to 42°C / min. Other steps are the same as specific embodiment 1 or 2.

[0047] Specific embodiment 4: This embodiment differs from Specific embodiments 1 to 3 in that the volume ratio of the dark red product to toluene in step 1 is 1:(3.5-4.5); the volume ratio of the dark red product to ether in step 1 is 1:(2.5-3.5). Other aspects are the same as Specific embodiments 1 to 3.

[0048] Specific embodiment 5: This embodiment differs from Specific embodiments 1 to 4 in that the concentration of the sulfuric acid solution in step 1 is 1.839 g / mL to 1.841 g / mL; and the volume ratio of the dark red product to the sulfuric acid solution in step 1 is 1:(0.45 to 0.55). Other steps are the same as Specific embodiments 1 to 4.

[0049] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that the drying in step 1 is carried out under vacuum at a temperature of 37° C. to 42° C. for 16 to 19 hours. Other aspects are the same as specific embodiments 1 to 5.

[0050] Specific embodiment 7: This embodiment differs from Specific embodiments 1 to 6 in that the concentration of concentrated sulfuric acid in step 2 is 1.839 g / mL to 1.841 g / mL. Other aspects are the same as Specific embodiments 1 to 6.

[0051] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the repeated precipitation of white particles from the filtrate in step 2 is specifically carried out according to the following steps: first adding NaCl to the filtrate, then adding 95% by mass ethanol, and repeating the process multiple times to precipitate white particles, thus obtaining the thiocalix[4]arene tetrasulfonate eluent; the volume ratio of the filtrate to the mass ratio of NaCl is 1 mL:(4.5-5.5) g; the volume ratio of the filtrate to the mass ratio of 95% by mass ethanol is 1:(1.5-3.5). Other aspects are the same as specific embodiments 1 to 7.

[0052] Specific embodiment 9: This embodiment uses a thiocalix[4]arene tetrasulfonate eluent, which acts as an eluent to simultaneously remove heavy metals and polycyclic aromatic hydrocarbons in soil.

[0053] Specific embodiment 10: This embodiment differs from specific embodiment 9 in that the heavy metal is one of copper, zinc, and lead, or a mixture of several thereof; and the polycyclic aromatic hydrocarbon is one of naphthalene, fluoranthene, and chrysene, or a mixture of several thereof. Other aspects are the same as specific embodiment 9.

[0054] The following examples are used to verify the beneficial effects of the present invention:

[0055] Example 1:

[0056] A method for preparing a thiocalix[4]arene tetrasulfonate eluent is carried out according to the following steps:

[0057] 1. Preparation of Thiacalixarene:

[0058] Under nitrogen protection, a mixture of p-tert-butylphenol (64.5 g, 0.43 mol), sulfur (27.5 g, 0.86 mol) and NaOH (8.86 g, 0.215 mol) and tetraethylene glycol dimethyl ether (19 mL) was stirred to obtain a mixture, which was maintained at 230° C. under nitrogen for 3 h to obtain a dark red product, which was cooled to room temperature, diluted with toluene and ether, and then a sulfuric acid solution was added to obtain a suspension, which was filtered, then recrystallized by adding chloroform, and finally dried to obtain thiacalixarene (TCA);

[0059] 2. Preparation of thiosulfonated calixarene:

[0060] 10g of thiacalixarene and 100mL of concentrated sulfuric acid were mixed, stirred at 100rpm and 80℃ for 24h, and finally cooled to obtain a mixed product. The mixed product was placed at 500cm 3 In ice water, the solid residue was removed by filtration to obtain a filtrate, and white particles were repeatedly precipitated from the filtrate to obtain a thiocalix[4]arene tetrasulfonate eluent (TSC4X);

[0061] In step 1, nitrogen is introduced at a rate of 0.25 g / s to remove the generated by-product hydrogen sulfide.

[0062] In step 1, the mixture was heated to 230° C. at a heating rate of 40° C. / min.

[0063] The volume ratio of the dark red product in step 1 to toluene is 1:4; the volume ratio of the dark red product in step 1 to ether is 1:3;

[0064] The concentration of the sulfuric acid solution in step 1 is 1.84 g / mL; the volume ratio of the dark red product in step 1 to the sulfuric acid solution is 2:1.

[0065] The drying in step 1 is specifically carried out under vacuum and at a temperature of 100° C. for 4 hours.

[0066] The concentration of the concentrated sulfuric acid described in step 2 is 1.84 g / mL.

[0067] The repeated precipitation of white particles from the filtrate in step 2 is specifically carried out according to the following steps: 500g of NaCl is first added to 100mL of the filtrate, and then 200mL of 95% by mass ethanol is added, and the process is repeated several times to precipitate white particles, thus obtaining the thiocalix[4]arene tetrasulfonate eluent.

[0068] In step 1, 11.5 g of thiacalixarene (TCA) was obtained with a yield of 39%.

[0069] The yield of thiocalix[4]arene tetrasulfonate eluent (TSC4X) in step 2 was 63%.

[0070] The synthetic route of thiacalixarene in step 1 of this embodiment is as follows:

[0071]

[0072] The synthetic route of the thiocalix[4]arene tetrasulfonate eluent in step 2 of this embodiment is as follows:

[0073]

[0074] Figure 1 This is the NMR spectrum of the thiocalix[4]arene tetrasulfonate eluent prepared in Example 1. As can be seen from the figure, two groups of NMR signals appear at 7.81ppm and 3.83ppm, representing the protons on the TSC4X aromatic ring and the hydroxyl group, respectively, proving the accuracy of the TSC4X structure.

[0075] Figure 2 This is the XRD diffraction spectrum of the thiocalix[4]arene tetrasulfonate eluent prepared in Example 1; it can be seen from the figure that the degree of crystallinity of TSC4X is poor and there is no obvious crystal feature.

[0076] Figure 3 This is the infrared spectrum of the thiocalix[4]arene tetrasulfonate eluent prepared in Example 1; as can be seen from the figure, TSC4X has an infrared spectrum of 3350 cm -1 The polymer OH stretching appeared at 1634 cm -1 The C=C stretching in the aromatic cavity was detected at 1091 cm -1 The peak of sulfonic acid group was detected at .

[0077] The TSC4X solution mentioned in the following experiments was specifically prepared by using DMSO solvent to prepare TSC4X as TSC4X solution. The soil described in the following experiments was collected from the flower bed in front of the library of the second campus of Harbin Institute of Technology. The surface soil with a depth of 0 cm-20 cm was taken, and a 5-point sampling method was adopted, namely A (East longitude: 126.684244, North latitude: 45.756578), B (East longitude: 126.684234, North latitude: 45.756526), C (East longitude: 126.684277, North latitude: 45.756571), D (East longitude: 126.684309, North latitude: 45.756638), and E (East longitude: 126.684352, North latitude: 45.756534). The sampler is a small shovel. The collected soil samples are placed in a sealed polyethylene bag and immediately brought back to the laboratory for cold storage. The soil is spread on newspaper to air dry, then ground in a mortar and passed through a 200nm sieve. After mixing, the soil is placed in a sample bottle for later use.

[0078] (1) Analysis of the efficiency of TSC4X in removing heavy metals:

[0079] Prepare soil contaminated with copper, zinc and lead at the same time: the corresponding compounds of the three heavy metals Zn, Cu and Pb are ZnSO4·7H2O, CuSO4·5H2O and Pb(NO3)2, which are added to the soil in the form of solutions and mixed thoroughly so that the soil contains copper, zinc and lead at the same time, and the concentrations of copper, zinc and lead in the soil are 250 mg / L respectively.

[0080] Figure 4 This is a test of the factors affecting the removal of copper, zinc and lead in soil by the thiocalix[4]arene tetrasulfonate eluent prepared in Example 1, including: a) degradation kinetics, b) the effect of TSC4X concentration, c) the effect of solid-liquid ratio, and d) the effect of pH value.

[0081] The effect of shaking time on the elution of heavy metals in soil was tested under the conditions of 0.3% TSC4X solution, a volume ratio of TSC4X solution to soil of 10 mL:1 g, a pH of 7.0, and a shaking speed of 100 rpm. The results are shown in Table 1. Figure 4 a). As can be seen from the figure, the removal rates of Cu, Zn, and Pb increased significantly in the first 60 minutes, reaching 75.2%, 74.8%, and 67.2% respectively. After 60 minutes, the reaction rate slowed down. Therefore, in actual engineering applications, in order to achieve a balance between removal efficiency and energy saving, the optimal elution time is usually 60 minutes.

[0082] Increasing the eluent concentration can significantly increase the content of TSC4X in the eluent, thereby improving the contact efficiency between TSC4X and heavy metals. Therefore, the concentration of the eluent is a major factor affecting the elution of heavy metals from soil by TSC4X. Under the conditions of a TSC4X solution volume to soil mass ratio of 10mL:1g, a pH of 7.0, and a shaking table speed of 100rpm, shaking for 2h, the effect of TSC4X solution concentration on the elution effect of heavy metals is detailed in [1]. Figure 4 b) When the mass percentage of TSC4X solution is 0.7%, the removal effect of copper and zinc is the best, reaching 82.1% and 78.2% respectively. When the mass percentage of TSC4X solution is 0.9%, the removal efficiency of lead is the highest, reaching 69.71%. At the same time, when the mass percentage of TSC4X solution is 0.05% to 0.3%, the removal efficiency of heavy metals by TSC4X increases rapidly. When the mass percentage of TSC4X solution exceeds 0.3%, the effect of TSC4X concentration on heavy metal removal is not very large. Considering the cost of TSC4X and other factors, the mass percentage of TSC4X solution can be selected to be 0.3%. According to the results of UV titration experiment ( Figure 10 ) It can be seen that the combination ratio of TSC4X and heavy metals is 1:1. Therefore, with the increase of concentration, the removal efficiency of heavy metals increases accordingly. When the mass percentage of TSC4X solution is higher than 0.7%, the increase in TSC4X concentration will inhibit the removal of copper ions. It is speculated that this may be due to the formation of a complex structure between high-concentration TSC4X and heavy metals in the soil and humus.

[0083] The solid-liquid ratio (the ratio of the mass of the soil to the volume of the TSC4X solution) is also one of the important factors affecting the leaching of contaminated soil. A low solid-liquid ratio will lead to insufficient contact between the eluent and the heavy metals in the contaminated soil, thereby affecting the removal efficiency. Increasing the solid-liquid ratio is equivalent to increasing the eluent dosage added per unit mass of contaminated soil. Therefore, as the solid-liquid ratio increases, the removal rate of heavy metals in the soil will also be improved to a certain extent. Under the conditions of a mass percentage of 0.3% TSC4X solution, a pH of 7.0, and a shaking table speed of 100 rpm, the shaker was shaken for 2 hours to determine the effect of different solid-liquid ratios on the heavy metal elution efficiency. The results are shown in the figure. Figure 4 c). As shown in the figure, the TSC4X elution efficiency for heavy metals increases with increasing solid-to-liquid ratio. When the solid-to-liquid ratio reaches 1:10 (the volume ratio of soil mass to TSC4X solution is 1g:10mL), the elution efficiency reaches its highest level, with removal rates of 75.6%, 74.3%, and 67.9% for copper, zinc, and lead, respectively. Subsequently, as the solid-to-liquid ratio increases, the elution efficiency decreases. Therefore, the optimal solid-to-liquid ratio for TSC4X heavy metal elution is 1:10 (the volume ratio of soil mass to TSC4X solution is 1g:10mL).

[0084] The pH value of the eluent is an important factor affecting the elution of heavy metals from soil. It affects the existing form of heavy metals in the eluent, the solubility of the eluent, and the adsorption and binding capacity of heavy metals in the soil. Under the conditions of a 0.3% mass percentage of TSC4X solution, a volume of TSC4X solution to soil mass ratio of 10mL:1g, and an oscillating shaker speed of 100rpm, the effect of different pH values on the elution efficiency of heavy metals was determined for 2 hours. The results are shown in Figure 4 d). As shown in the figure, under weakly acidic and neutral conditions, heavy metals have a higher affinity for sulfur atoms due to the high stability of heavy metal-S bonds caused by the electron shift of heavy metals to sulfur atoms. Therefore, under weakly acidic and neutral conditions (pH 5-7), the elution efficiency is high. At pH 7, the elution efficiencies for copper, zinc, and lead are 75.6%, 74.3%, and 67.9%, respectively. However, as the acidity increases, the protonation of OH groups hinders the binding of heavy metals to TSC4X. Furthermore, since heavy metal contaminants are less likely to bind under acidic conditions, the removal efficiencies of TSC4X for copper, zinc, and lead decrease to 63%, 61%, and 53%, respectively, at pH 4. This also provides a new approach to TSC4X-heavy metal recovery.

[0085] (2) Analysis of the efficiency of TSC4X in removing PAHs:

[0086] Preparation of soil contaminated with naphthalene, fluoranthene and pyrene: 50 mg of naphthalene, 50 mg of fluoranthene and 50 mg of pyrene were dissolved in 200 mL of dichloromethane solution at the same time, and shaken for 48 hours until fully mixed to obtain a mixed solution of polycyclic aromatic hydrocarbons. The mixed solution of polycyclic aromatic hydrocarbons was poured into 500 mg of sieved soil, shaken thoroughly, and ventilated in a fume hood until the organic solution was completely evaporated. Finally, it was aged in the dark for 6 months.

[0087] Figure 5 The test results show that the factors affecting the removal of naphthalene, fluoranthene and pyrene from soil by the thiocalix[4]arene tetrasulfonate eluent prepared in Example 1 are as follows: a) degradation kinetics, b) effect of TSC4X concentration, c) effect of solid-liquid ratio, and d) effect of pH value.

[0088] The effect of shaking time on the elution of PAHs from soil was tested under the conditions of 0.3% TSC4X solution, a TSC4X solution volume to soil mass ratio of 10 mL:1 g, a pH of 7.0, and a shaking speed of 100 rpm. The results are shown in Table 1. Figure 5a). The trend is similar to the kinetic experiment for heavy metals. In the first 2 hours, the removal rate of PAHs increased significantly. After 2 hours, the removal rates of the three PAHs slowly increased, ultimately reaching 52.6%, 44.6%, and 42.6% for naphthalene, fluoranthene, and pyrene, respectively. As the number of PAH rings increases, the elution effect gradually decreases. This is because the guest molecules primarily bind to TSC4X in a polar aqueous environment through hydrophobic interactions. The octanol partition coefficients for naphthalene, fluoranthene, and pyrene are 3.47 Sol / mol·m -3 、2.93Sol / mol·m -3 and 2.83Sol / mol·m -3 , the hydrophobicity decreases in sequence, so the ability to bind to TSC4X decreases in sequence and the binding efficiency decreases.

[0089] Under the conditions of a TSC4X solution volume to soil mass ratio of 10 mL:1 g, a pH of 7.0, and a shaking speed of 100 pm, the shaking was carried out for 2 h. The effect of TSC4X concentration on the elution effect of PAHs is detailed in [1]. Figure 5 b). As can be seen from the figure, the concentration has no significant effect on the removal efficiency of PAHs. When the mass percentage of TSC4X solution is 0.3%, the removal efficiency of naphthalene is the highest, 52.3%; when the mass percentage of TSC4X solution is 0.5%, the removal efficiency of fluoranthene reaches the highest, 45.8%; and the highest removal efficiency of pyrene, 44.5%, can only be achieved when the mass percentage of TSC4X solution is 0.7%.

[0090] The solid-to-liquid ratio (the ratio of soil mass to TSC4X solution volume) is another parameter that affects soil elution efficiency. The effects of different solid-to-liquid ratios on the elution efficiency of PAHs were determined for 2 hours using a 0.3% mass percent TSC4X solution, a pH of 7.0, and a shaker speed of 100 rpm. The results are shown in Table 1. Figure 5 c); The results show that the leaching efficiency increases with the increase of the solid-liquid ratio. When the solid-liquid ratio is 1:2, the treatment efficiency of naphthalene, fluoranthene and pyrene are 29.7%, 19.6% and 7.8%, respectively. When the solid-liquid ratio is 1:20 (the volume ratio of the mass of the soil to the TSC4X solution is 1g:20mL), the removal efficiency of naphthalene, fluoranthene and pyrene reaches 55.2%, 51.6% and 41.3%. However, after the solid-liquid ratio is higher than 1:20, the increase in the solid-liquid ratio cannot significantly improve the leaching efficiency. A lower solid-liquid ratio may lead to enhanced adsorption of TSC4X to the soil. This is because the negatively charged soil particles and the macromolecular organic matter adsorbed on the soil particles will not combine with TSC4X. However, due to the loose and porous structure of the soil, a small amount of TSC4X will inevitably be adsorbed in the soil. At the same time, fluorescence and UV titration experiments ( Figure 10) shows that there is a certain stoichiometric relationship between TSC4X and PAHs. Therefore, the lower the solid-liquid ratio, the lower the PAH degradation efficiency. As the solid-liquid ratio exceeds 1:20, the increase in the solid-liquid ratio has a less significant effect on PAH removal. Therefore, a water-to-soil ratio of 1:10 is recommended in actual engineering practice.

[0091] Under the conditions of 0.3% mass percentage of TSC4X solution, the volume of TSC4X solution and the mass ratio of soil was 10mL:1g and the shaking speed was 100rpm, the shaking was carried out for 2h to determine the effect of different pH values on the elution efficiency of polycyclic aromatic hydrocarbons. The results are shown in Figure 5 d). Three pH values commonly used in practical engineering applications were selected: 6, 7, and 10. The results showed that under acidic conditions (pH 6.0), TSC4X achieved removal efficiencies of 43.9%, 36.5%, and 32.6% for naphthalene, fluoranthene, and pyrene, respectively. Under neutral conditions (pH 7.0), the removal efficiencies were 52.6%, 44.4%, and 42.1%, respectively. Under alkaline conditions, TSC4X achieved removal efficiencies of 53.9%, 47.6%, and 45.9%, respectively, for naphthalene, fluoranthene, and pyrene. Under acidic conditions, the ionization of the phenolic groups at the lower edge of TSC4X strengthens hydrogen bonds within the TSC4X molecule, reducing its ability to bind to guest molecules. Furthermore, under acidic conditions, the sulfonate converts to sulfonic acid, weakening the electron-withdrawing ability of the upper edge of TSC4X to the cavity. This increases the electrostatic charge of the cavity, thus reducing its ability to bind to guest molecules through electrostatic interactions.

[0092] (3) Characterization and analysis of TSC4X removal of heavy metals and polycyclic aromatic hydrocarbons:

[0093] Taking TSC4X combined with naphthalene, copper, and both naphthalene and copper as examples, the binding modes of TSC4X with heavy metals and organic matter were analyzed, and FTIR, XRD, NMR, and SEM experiments were conducted.

[0094] 0.2 mol of TSC4X and 0.2 mol of naphthalene were dissolved in 50 mL of DMSO to obtain a TSC4X-naphthalene solution; 0.2 mol of TSC4X and 0.2 mol of copper were dissolved in 50 mL of deionized water to obtain a TSC4X-copper solution; 0.2 mol of TSC4X, 0.2 mol of naphthalene and 0.2 mol of copper were dissolved in 50 mL of water / methanol solution (volume ratio of 1:1) to obtain a TSC4X-naphthalene-Cu solution; the mixture was shaken in a light-proof shaker at a speed of 100 rpm and a temperature of 35° C. until the TSC4X-naphthalene solution, TSC4X-copper solution and TSC4X-naphthalene-Cu solution were clarified, the solution after complete reaction was rotary evaporated to about 5 mL, the solid-liquid mixture after rotary evaporation was placed in a petri dish and vacuum dried until powder was formed to obtain a TSC4X-naphthalene complex, a TSC4X-copper complex and a TSC4X-naphthalene-copper complex, and the complex was analyzed by infrared, X-ray, nuclear magnetic resonance and scanning electron microscopy.

[0095] Figure 6 The infrared spectra of the thiocalix[4]arene tetrasulfonate eluent, naphthalene, TSC4X-naphthalene complex, TSC4X-copper complex, and TSC4X-naphthalene-copper complex prepared in Example 1 are shown in FIG. As can be seen from the figure, the infrared spectrum of TSC4X undergoes significant changes after it is combined with naphthalene. After the TSC4X-naphthalene complex is formed, TSC4X has a peak at 3350 cm -1 The “polymer” OH stretching produces a broad and intense spectral band, which shifts to 3386 cm at naphthalene. -1 At the same time, the hydroxyl group on TSC4X is at 3472 cm -1 There is a small and sharp peak at 10 cm (representing the OH bond) -1 At the same time, the generation of TSC4X-naphthalene complexes results in a decrease in the intensities of the two peaks representing the “polymer” OH stretching and OH bonding. The introduction of naphthalene molecules also makes the two peaks more separated, and even a peak covering 3697 cm -1 ~3100cm -1 This may be due to the OH-π interaction between the OH groups of the TSC4X-naphthalene complex and the naphthalene molecules embedded near the lower edge of the cavity. This weak interaction may also lead to the reduction of the OH tensile strength. At the same time, at about 800 cm -1 The CH bond outside the aromatic ring plane disappears, indicating that the CH is restricted from the plane due to the presence of TSC4X-naphthalene complex. More notably, at 1662 cm -1 The C=C stretching in the aromatic cavity and the 1123 cm -1 The OH groups observed at about 4 cm -1This slight blue shift may be partly due to the fact that the electron-rich naphthalene can easily enter the cavity with negative π potential of TSC4X caused by the electron-withdrawing sulfonic acid group.

[0096] In the TSC4X-naphthalene and TSC4X-naphthalene-Cu complexes, the -1 The Cu-S bond appears at the bottom, and the OH bond strength is weakened, the separation degree is reduced, and the red shift occurs, which also proves that copper mainly forms Cu-S bonds with S at the bottom edge of TSC4X, and the OH group at the bottom edge of TSC4X assists in coordination through hydrogen bonds.

[0097] Figure 7 XRD diffraction patterns of the thiocalix[4]arene tetrasulfonate eluent, naphthalene, TSC4X-naphthalene complex, TSC4X-copper complex, and TSC4X-naphthalene-copper complex prepared in Example 1; compared with the XRD pattern of TSC4X, the intensity of the crystal peak of the TSC4X-naphthalene complex weakened and broadened, and the background noise also increased significantly. These differences may be due to the fact that the introduction of naphthalene reduced the crystallinity of TSC4X. This observation is also consistent with the result that the interaction between the guest and the host may cause the XRD peak to broaden and decrease. Although the TSC4X-naphthalene complex did not develop its own unique XRD pattern after formation, TSC4X and the newly formed complex have some of the same characteristic peaks, and the characteristic peaks even have only slight shifts. These similarities may be due to the fact that the introduction of naphthalene did not completely change the molecular structure of TSC4X, and theoretical calculations can also confirm this speculation. However, with the introduction of copper ions, the crystal structure of TSC4X-copper is very different from that of TSC4X itself. The change in the crystal structure is caused by the obvious Jahn-Teller distortion caused by the geometric shape of the copper ion metal coordination, which changes the position of the S and O bonds at the lower edge of TSC4X, and then causes the overall space to be distorted, and the crystal structure changes significantly. The crystal structure of the composite structure formed by TSC4X and copper is similar to that of Na2Cu(SO4)2(H2O)2(PDF#70-0884) (as shown in the figure) The crystal structure is a typical octahedral coordination structure for copper ions, the most common structure for Jahn-Teller distortion. Therefore, the occurrence of Jahn-Teller distortion is also confirmed from the perspective of the TSC4X-copper crystal structure. The XRD pattern of the TSC4X-copper-naphthalene crystal shows an intermediate pattern between TSC4X-naphthalene and TSC4X-copper. It is speculated that the electron-withdrawing effect of the naphthalene molecules on the TSC4X cavity may suppress the Jahn-Teller distortion caused by the introduction of copper ions, making the distortion of the overall TSC4X molecular structure slightly less obvious. This view is also supported by the structural optimization of TSC4X-naphthalene-copper.

[0098] Figure 8 The NMR hydrogen spectra of the thiocalix[4]arene tetrasulfonate eluent, naphthalene and TSC4X-naphthalene complex prepared in Example 1; the chemical position values of TSC4X, naphthalene and the TSC4X-naphthalene complex with a molar ratio of 1:1 were analyzed to further reveal the binding mechanism of the three. Ar-H and Ar-OH are the aromatic protons and aromatic hydroxyl groups of TSC4X, respectively, and aH, bH and cH represent the protons at different positions of the naphthalene molecule, respectively. Before the NMR analysis of TSC4X and its complex, it should be considered that the Ar-H at 7.81ppm is very close to the naphthalene protons at 7.91ppm and 7.52ppm, so the TSC4X signal may cover the influence of some naphthalene proton signals. Due to the π-π interaction between the aromatic cavity of TSC4X and naphthalene, the naphthalene protons will undergo a shielding effect during the binding process with TSC4X, causing its chemical shift to move to the high field. After the complex is formed, the naphthalene molecule not only moves to the high field, but also a new peak appears. This phenomenon rarely occurs in the formation of the complex. It is speculated that the embedding of the naphthalene molecule may lead to hydrogen bonding between the lower edge of naphthalene and TSC4X, resulting in a stronger shielding effect at the cH position, thus disrupting the spatial symmetry of the naphthalene and allowing the emergence of a new positional hydrogen at the lower edge of naphthalene. This result is consistent with the FTIR spectrum. After TSC4X inclusion of naphthalene, the Ar-H peak also broadens significantly. This broadening of the TSC4X aromatic proton peak may be due to the complexation of the naphthalene molecule causing local fluctuations in the TSC4X aromatic core, resulting in thermal tumbling and relaxation. In contrast to the upshift of the naphthalene protons, the Ar-H and Ar-OH protons at 7.81 ppm and 3.83 ppm in the TSC4X molecule shift downfield by 7.84 ppm and 5.33 ppm, respectively. This phenomenon also confirms the host-guest inclusion relationship between TSC4X and naphthalene.

[0099] Figure 9 Scanning electron microscope images of the thiocalix[4]arene tetrasulfonate eluent and its composite prepared in Example 1: (a) TSC4X scale 200nm, (b) TSC4X scale 2μm, (c) TSC4X-Cu scale 200nm, (d) TSC4X-copper scale 2μm and S, O, Cu element distribution diagram, (e) TSC4X-naphthalene scale 200nm, (f) TSC4X-naphthalene scale 2μm, (g) TSC4X-copper-naphthalene scale 200nm, (h) TSC4X-copper-naphthalene scale 2μm and S, O, Cu element distribution diagram; TSC4X, TSC4X-naphthalene, TSC4X-copper, TSC4X-copper-naphthalene composite were further observed by SEM to observe the structure and morphology of the two particles. Figure 9(e, f) shows that when naphthalene molecules exist, the particle size of the complex decreases from about 0.2μm to 0.8μm to 0.1μm to 0.5μm, and the surface of the complex becomes rougher than that of TSC4X crystals. At the same time, the crystal structure of the complex also undergoes significant changes. TSC4X particles are originally formed by 3-15 irregular polygonal thin plates, and their crystal morphology is poor and uneven. After the formation of the complex, the morphology of the crystal changes to plate-like particles, and this phenomenon can be confirmed by XRD spectra. At the same time, the TSC4X-naphthalene composite crystals appear smaller, with clear boundaries, and the morphology is similar to that of TSC4X crystals after 90° rotation. Figure 9 (c, d) show that the structure of TSC4X-Cu becomes a distinct rod. EDS shows that the positions of sulfur, oxygen, and copper elements have a certain degree of overlap, indicating that copper ions are mainly coordinated by combining with S and O. Figure 9 As shown in Figures (g,h), the morphological changes in TSC4X-copper-naphthalene are most pronounced. The complex lacks a clear crystal form, exhibits a rough surface, and exhibits a distinct graininess. Unlike TSC4X-copper and TSC4X-naphthalene, TSC4X-copper-naphthalene lacks a crystalline structure. EDS analysis of the three composite structures reveals that the S and O elements still overlap with the copper ions, indicating that TSC4X retains the ability to bind copper while also binding to naphthalene.

[0100] In order to determine the stoichiometry of the binding of TSC4X with naphthalene, TSC4X with copper, and TSC4X with both naphthalene and copper, titration experiments were performed to analyze and determine the stoichiometry of the binding by varying the molar ratios of TSC4X with different guest molecules.

[0101] Figure 10 Titration diagram of the thiocalix[4]arene tetrasulfonate eluent and its complex prepared in Example 1, (a) UV spectra of TSC4X-naphthalene complex solutions with different molar ratios, (b) UV spectra of TSC4X and naphthalene after correction by the inverse ratio method, and the relationship between the maximum absorbance of TSC4X and naphthalene with different molar ratios, (c) UV spectra of TSC4X and copper, (d) UV spectra of TSC4X-Cu 2+ Metrology analysis, (e)TSC4X-naphthalene-Cu 2+ Fluorescence spectra, (f) copper ion concentration and TSC4X-naphthalene-Cu 2+ Maximum fluorescence spectrum relationship of the composite structure;

[0102] The stoichiometry and binding constants of the interaction between TSC4X and polycyclic aromatic hydrocarbons were determined using the continuous variation method (Job's Plot method). First, TSC4X and naphthalene were dissolved in DMSO to obtain a TSC4X-naphthalene solution, and the molar ratio of naphthalene / (TSC4X+naphthalene) in the TSC4X-naphthalene solution was (1-9):10=0.1-0.9. The solution was shaken in a light-proof shaker at a speed of 100 rpm and a temperature of 30°C until TSC4X and naphthalene fully reacted to obtain a TSC4X-naphthalene complex solution. The TSC4X-naphthalene complex solutions with different molar ratios were analyzed by ultraviolet spectroscopy, and a curve showing the relationship between absorbance and the molar ratio of TSC4X was plotted. To overcome the interference of TSC4X on the absorbance of the TSC4X-naphthalene complex, the inverse ratio method was used to divide the spectrum of the TSC4X-naphthalene complex by the ultraviolet spectrum of TSC4X, using a scale factor of 10 and a wavelength increment of 4 nm. The stoichiometric ratio of the TSC4X-naphthalene complex can be estimated using the continuous variation method, see Figure 10 (b), the maximum peak was observed when the molar ratio of naphthalene / (TSC4X + naphthalene) in the TSC4X-naphthalene solution was 0.5, indicating that a 1:1 complex was formed between TSC4X and naphthalene.

[0103] A TSC4X-copper solution was obtained by dropwise adding 0.01 mM to 0.15 mM copper ions to a 0.1 mM TSC4X solution, wherein the molar ratio of Cu to TSC4X in the TSC4X-copper solution was (0.01 to 0.15):0.1=(0.1 to 1.5):1. The solution was shaken in a light-proof shaker at a speed of 100 rpm and a temperature of 30°C until TSC4X and copper fully reacted to obtain a TSC4X-copper complex solution, which was also subjected to UV spectroscopy analysis ( Figure 10 c), and then the stoichiometric constants of TSC4X and copper ions were determined using the specific molar method ( Figure 10 d), due to the Cu 2+ When / TSC4X reaches 1.0, there is an obvious slope change, so it can be inferred that TSC4X and copper are also matched in a 1:1 manner.

[0104] Since naphthalene ions and copper ions are important for TSC4X-naphthalene-Cu 2+ In order to eliminate the influence of the overlap and accumulation of the UV spectra and to eliminate the interference of the composite structure of the three, and because naphthalene and copper do not have obvious fluorescence, fluorescence spectroscopy was used to test the Cu in TSC4X-naphthalene solution with a fixed concentration of 0.1mM. 2+ Fluorescence spectrum changes at concentrations of 0mM to 0.1mM ( Figure 10e), and according to the fluorescence spectrum results, a graph was drawn with the abscissa being the concentration of copper ions and the ordinate being the maximum absorbance ( Figure 10 f), since the slope is approximately 1, the basic binding stoichiometry of TSC4X with naphthalene and copper is determined to be 1:1:1.

[0105] (4) Computational chemical analysis of TSC4X for the removal of heavy metals and polycyclic aromatic hydrocarbons:

[0106] Figure 11 The structural optimization diagrams of the thiocalix[4]arene tetrasulfonate eluent and its complex prepared in Example 1, (a), (b) TSC4X top view and front view, (c) naphthalene, (d), (e) TSC4X-naphthalene top view and front view, (f), (g) TSC4X-copper front view and top view, (h) TSC4X-copper-naphthalene; the optimized geometric structures of TSC4X, naphthalene and their complexes were generated by M06-2X hybrid exchange correlation function and 6-31G (d, p) algorithm basic set. The TSC4X structure with the lowest energy presents a cone conformation, with the sulfonate group on the upper edge and the phenolic OH group on the lower edge connected by sulfide, as shown in FIG. Figure 11 (a, b). In addition, based on the distance between O1 and O3, the size of the lower edge is Therefore, from the perspective of size compatibility, TSC4X can easily bind to naphthalene molecules. In addition, the docking of naphthalene with TSC4X is as follows Figure 11 As shown in (d, e), naphthalene is only partially contained in the TSC4X cavity. This calculation result is very consistent with the NMR spectrum. The lowest negative binding energy (ΔG) of the most stable TSC4X-naphthalene configuration is calculated to be -253.6 kcal / mol. It can be seen that the complexation of naphthalene significantly changes the size of the TSC4X cavity. For example, the length of H1-O2 and S1-S2 of the TSC4X-naphthalene complex is calculated. The distance of the intramolecular hydrogen bond on the upper and lower edges formed by the hydroxyl group and the sulfonic acid group is stretched by about 0.18 and 0.60, respectively, compared with TSC4X alone. The expansion of the TSC4X cavity can be well explained by the steric hindrance between the flexible TSC4X cavity and naphthalene, and the adjustment of the cavity size has also been observed in other studies.

[0107] TSC4X and copper structure optimization Figure 11 (f, g), after TSC4X combines with copper ions, a more obvious deformation occurs. This deformation may be caused by the Jahn-Teller theorem, especially for high-spin Cu (the ion electronic configuration is 3d 9. In an octahedral symmetric environment, the 3d orbital is split into two groups: three t2g orbitals and two eg orbitals. For Cu ions, the t2g orbital is completely filled, while there is a single electron in the eg orbital. This single electron causes degeneracy in the eg orbital, resulting in Jahn-Teller distortion. In order to reduce energy, the octahedral structure is distorted, which is manifested in that the distance between the TSC4X ligand and the copper atom becomes longer, while the others become shorter. This theory also explains the phenomenon that TSC4X has the highest removal rate for copper ions, and at the same time determines that the ΔG of the junction between TSC4X and copper ions is -112.4 kcal / mol.

[0108] Compared with the composite product of TSC4X and copper, TSC4X-Cu-naphthalene did not undergo obvious distortion. It is speculated that this may be because the attraction of the electron-deficient outer edge of naphthalene to the negative potential outer wall of TSC4X hinders its structural change.

[0109] Figure 12 The van der Waals surface electrostatic distribution diagram of the thiocalix[4]arene tetrasulfonate eluent and its complex prepared in Example 1, (a) TSC4X, (b) naphthalene, (c, d) TSC4X-naphthalene top view and front view, (e, f) TSC4X-Cu-naphthalene top view and front view, (g) TSC4X-Cu front view; molecular electrostatic potential on the VdW surface to analyze the binding site of TSC4X and the charge distribution in TSC4X-naphthalene, TSC4X-Cu, and TSC4X-Cu-naphthalene complexes. Due to the high electronegativity and high electron absorption of the sulfonic acid group, the electronic potential of the entire vdW surface is negative, with red indicating a higher electrostatic potential and blue indicating a relatively smaller electrostatic potential. It is obvious that the sulfonic acid group on the upper edge of TSC4X has the most negative electrostatic formula, with an electronegativity range of -9.64 to 9.79 eV, located around the oxygen atom of the sulfonate group. Since the π electron density of the TSC4X aromatic cavity is attracted by the sulfonic acid groups, a less electronegative region is formed around the TSC4X cone, and even a Vmax region of approximately -7.17 eV can be found at the lower edge of TSC4X ( Figure 12 a). In summary, the active binding site is likely located at the lower or upper edge of the TSC4X cavity, with the exact location depending on the nucleophilicity and electrophilicity of the guest molecule.

[0110] Figure 12(b) illustrates the charge density distribution of the naphthalene molecule. The center of the naphthalene molecule forms an adjacent π bond with a negative potential, while the blue area around the naphthalene molecule represents an electron-deficient positive potential, with a maximum positive potential of 14.33 eV and a maximum negative potential of -17.16 eV. In order to obtain the maximum electronic attraction, the electron-rich binding site outside the naphthalene molecule is located in the middle of the four Vmin sites on the upper edge of TSC4X (keeping the distance to the four Vmin consistent). Considering that there is a strong electronic attraction between TSC4X and the unsaturated negative repulsive region of the aromatic ring of naphthalene, the negative potential part of the naphthalene molecule facing the sulfonic acid group makes the upper edge of TSC4X become more separated, and even forms a rhombus, thereby expanding the flexible TSC4X cavity. From Figure 12 Starting from the surface of the TSC4X-naphthalene complex, upon binding to naphthalene, the TSC4X-naphthalene complex exhibits a slightly negative potential. Only 40% of the vdW surface exhibits a relatively low negative potential (<7.5 eV), while 90% of the TSC4X complex possesses a more negative potential. Furthermore, due to the nucleophilic sulfonic acid group's attraction to the π electron density of the naphthalene molecule, a significant charge transfer occurs between TSC4X and naphthalene. The negative Mep on the TSC4X VdW surface can also act as a hydrogen acceptor when interacting with guest molecules. IGMH analysis allows for a more graphical interpretation of host-guest hydrogen bonding.

[0111] The electrostatic diagram of TSC4X bonding with copper is shown below. Figure 12 As shown in (g), since the copper atom itself has a strong nucleophilicity, it is easy to attack the lower edge of the TSC4X molecule with electrophilicity. It is worth noting that after the copper atom binds to the lower edge of TSC4X, the electrostatic formula of the entire system increases, and the electrostatic potential of the lower edge changes from -6eV to 0eV. This phenomenon may be explained by the Lewis acid-base theory. The copper ion with Lewis acidity forms a complex with the phenolic hydroxyl group with Lewis basicity, making the electrostatic formula of this area become 0, and the negative π potential of the cavity increases.

[0112] The van der Waals surface electrostatic equation of the composite structure of TSC4X, naphthalene and copper is as follows Figure 12 As shown in Figures (e, f), combined with the results of TSC4X reacting with naphthalene alone and copper alone, we can see that naphthalene and copper bind to the negative π potential cavity and the canonical lower edge of TSC4X, respectively. The introduction of the electrophilic copper ion may increase the electrophilicity of the entire benzene ring cavity, thereby better binding to the nucleophilic naphthalene molecules in the system. As a result, after binding to the copper ion and then to naphthalene, the benzene ring cavity of TSC4X becomes more compact. Since the cavity size of calixarene is closely related to the shape and size fit of the complex organic matter, it is clear that the introduction of the electrophilic copper ion makes the entire aromatic cavity more suitable for containing naphthalene molecules, which may improve the removal efficiency of TSC4X for naphthalene.

[0113] Figure 13The weak interaction between the thiocalix[4]arene tetrasulfonate eluent prepared in Example 1 and naphthalene, a) is the weak interaction between TSC4X and naphthalene, and b) is the scatter plot of the weak interaction; According to the IGM theory, when sign(λ2)ρ is close to -0.04, hydrogen bonding occurs, and when sign(λ2)ρ is close to -0.2, it represents intramolecular interaction, and a positive sign(λ2)ρ indicates that steric repulsion occurs. It can be seen that TSC4X and naphthalene are mainly bound by non-covalent bonds, and also have certain hydrogen bonds and electrostatic repulsion. IGMH also intuitively verifies the experimental characterization analysis of the binding of TSC4X and naphthalene, which also proves the previous speculation that naphthalene mainly enters the cavity of TSC4X through hydrophobic interaction.

[0114] Figure 14 The molecular orbital topology of the thiocalix[4]arene tetrasulfonate eluent prepared in Example 1, combined with naphthalene, participates in the main absorption band electronic transition; the electron transfer of the TSC4X-naphthalene complex is further explained by time-dependent density functional theory (TDDFT). The theoretical absorption spectrum of the topological structure of the selected molecular orbitals participating in the host-guest electronic transition is shown in Table 1, and four main absorption bands at 278.86, 272.66, 266.12, and 258.98 nm are calculated, with oscillator intensities of 0.0391, 0.41440, 0.1957, and 0.04, respectively. The band at 279.86 nm originates from the π-π interaction between the naphthalene molecule and the TSC4X hydrophobic cavity, because the HOMO is completely present on the naphthalene molecule, while the LUNO+3 is located in the cavities of naphthalene and TSC4X. The HOMO+1 to LUMO+4 and HOMO+3 to LUMO+2 orbitals (mainly contributing to the spectral bands at 272.66 and 258.98 nm) are both due to hydrogen bonds between the hydroxyl group and the part of the naphthalene molecule that is directly bound to TSC4X. This is because the most important electronic transitions from (HOMO+1, HOMO+3) to (LUMO+4, LUMO+2) occur on the phenolic OH group and the part of the naphthalene molecule that is bound to TSC4X. This phenomenon clearly indicates that there is a hydrogen bond between TSC4X and naphthalene. Experimental results such as FTIR and NMR also confirm the existence of synergistic hydrogen bonding interactions between the hydroxyl groups.

[0115] Table 1 Theoretical excitation bands, electron orbital transitions and their contributions of TSC4X combined with naphthalene

[0116]

[0117]

[0118] Figure 15The molecular orbital topology of the thiocalix[4]arene tetrasulfonate eluent prepared in Example 1 and copper participating in the main absorption band electronic transition; from the structural optimization and electrostatic result analysis, it can be seen that the combination of TSC4X and copper is mainly caused by the co-coordination of copper ions with the lower oxygen and sulfur atoms of TSC4X. This conclusion is more intuitively reflected in the electron cloud transition of TSC4X-copper ions. Under the conditions of excitation wavelengths of 510.44nm and 497.05nm, through the topological analysis of its TDDFT results, it can be seen that the electronic orbital transition of TSC4X from HOMO to LUMO is mainly reflected in the transfer of TSC4X aromatic cavity to the lower S atom and OH lower edge, while the electronic transitions from HOMO+27 to LUMO, HOMO+26 to LUMO, and HOMO to LUMO+2 are mainly distributed on the coordination bonds between copper ions and S and O atoms. This conclusion further confirms that copper ions can combine with TSC4X at its lower edge with S atoms and oxygen atoms.

[0119] Table 2 Theoretical excitation bands, electron orbital transitions and their contributions of TSC4X combined with copper

[0120]

[0121] (5) The soil was shaken and leached under the conditions of different mass percentages of TSC4X solution, a volume ratio of TSC4X solution to soil of 10 mL:1 g, a pH of 7.2, and a shaking table speed of 100 rpm for 24 h.

[0122] Table 3 Changes of humus in contaminated soil after leaching at different concentrations

[0123]

[0124] Table 4 Changes in mineral content in contaminated soils leached at different concentrations

[0125] TSC4X concentration Total nitrogen g / Kg Total phosphorus g / Kg Potassium ion g / Kg Magnesium ion g / Kg Original value 1.85 1.08 18.95 19.87 purified water 1.42 1.02 17.71 18.48 0.03%TSC4X 1.21 0.96 18.74 16.29 0.3%TSC4X 1.19 0.85 18.74 15.46

[0126] Different concentrations of thiocalix[4]arene tetrasulfonate were selected to conduct leaching experiments on heavy metal-polycyclic aromatic hydrocarbons contaminated soil. The results showed that thiocalix[4]arene tetrasulfonate did not reduce the content of various humus in the soil, and the content of nutrients such as nitrogen and phosphorus, as well as potassium ions and magnesium ions in the soil did not change significantly.

[0127] The impact of TSC4X on soil ecology was determined by analyzing the changes in microbial respiration in different soils (original soil, low-concentration contaminated soil, medium-concentration contaminated soil, and high-concentration contaminated soil) after the addition of TSC4X. The soils were shaken and leached for 2 hours using different mass percentages of TSC4X solution, a TSC4X solution volume to soil mass ratio of 10 mL:1 g, a pH of 7.2, and a shaking shaker speed of 100 rpm. The concentrations of naphthalene, fluoranthene, and pyrene in the low-concentration contaminated soil were all 10 mg / kg, the concentrations of naphthalene, fluoranthene, and pyrene in the medium-concentration contaminated soil were all 100 mg / kg, and the concentrations of naphthalene, fluoranthene, and pyrene in the high-concentration contaminated soil were all 1000 mg / kg. 10.00 g of each of the four soils before and after TSC4X leaching were weighed and placed in a petri dish. The soils were evenly distributed and the soil moisture content was adjusted to 65%. 5 mL of 1 mol·L -1 Seal the culture dish with a sealing film and incubate at room temperature for 24 h before removing the sealing film. Pour the liquid in the culture dish into a 25 mL conical flask. Rinse the sealing film three times with a washing bottle and wipe it dry with filter paper. Pour the rinsed liquid into the conical flask and add 4 mL of 1 mol·L -1 barium chloride solution, add 1 drop of phenolphthalein solution, shake well and use 0.05mol·L -1 Titrate with HCl solution until the red color disappears. Continue to culture for 14 days, measure every 24 hours, and repeat three times for each sample.

[0128] Figure 16 The dynamic changes of respiration intensity before and after leaching different soils with the thiocalciferol [4] aromatic tetrasulfonate eluent prepared in Example 1, (a) original soil, (b) low-concentration contaminated soil, (c) medium-concentration contaminated soil, (d) high-concentration contaminated soil; As shown in the figure, the respiration rate of microorganisms in uncontaminated soil and three contaminated soils was affected by 0.03% by mass TSC4X solution and 0.3% by mass TSC4X solution. During the 0th to 14th day of incubation, the respiration rate of soil microorganisms first increased significantly and then decreased sharply, which means that the soil repaired by TSC4X leaching continued to emit CO2 during the entire incubation process. During the 14-day incubation period, the respiration rate of soil microorganisms treated with 0.03% by mass TSC4X solution and 0.3% by mass TSC4X solution was basically the same: the release of CO2 increased significantly in the first 5 days, gradually slowed down from 5th to 10th day, and then remained basically stable, which was basically consistent with the trend of the initial soil. In the original soil ( Figure 16 a) The maximum CO2 release among the three soils occurred at 4 days. The CO2 release from the 0.3% TSC4X leaching treatment was 126.10 mg·kg -1 ; Low concentration contaminated soil ( Figure 16b) The soil treated with 0.3% TSC4X showed the highest respiration rate at 5 days, with a CO2 release of 291.25 mg·kg -1 ; Medium concentration contaminated soil ( Figure 16 c) Similarly, the soil treated with 0.3% TSC4X had a maximum respiration rate of 144.12 mg kg -1 ; High concentration contaminated soil ( Figure 16 d) The soil treated with 0.3% TSC4X reached the maximum CO2 release rate of 291.25 mg kg after 7 days. -1 The above analysis showed that TSC4X leaching remediation did not affect the soil respiration rate, and treatment with different concentrations of TSC4X had no significant effect on the changes in soil respiration intensity.

Claims

1. Application of a thiocalix[4]arene tetrasulfonate eluent, characterized in that It is used as a leaching agent to simultaneously remove heavy metals and polycyclic aromatic hydrocarbons in the soil; the polycyclic aromatic hydrocarbons are one or a mixture of naphthalene, fluoranthene and fluoranthene; The thiocalix[4]arene tetrasulfonate eluent is prepared according to the following steps:

1. Preparation of Thiacalixarene: Under nitrogen protection, a mixture of p-tert-butylphenol, sulfur, and NaOH is stirred and mixed with tetraethylene glycol dimethyl ether to obtain a mixture, and the mixture is maintained at a temperature of 228° C. to 233° C. and nitrogen is introduced for 2.5 hours to 4.5 hours to obtain a dark red product, and the dark red product is cooled to room temperature, diluted with toluene and diethyl ether, and then a sulfuric acid solution is added to obtain a suspension, and the suspension is filtered, and then chloroform is added for recrystallization, and finally dried to obtain thiacalixarene; The molar ratio of p-tert-butylphenol to sulfur in the mixture is 1:(1.9-2.1); the molar ratio of p-tert-butylphenol to NaOH in the mixture is 1:(0.45-0.55); the volume ratio of NaOH to tetraethylene glycol dimethyl ether in the mixture is 1 mol:(85-100) mL; 2. Preparation of thiosulfonated calixarene: Mix thiacalixarene and concentrated sulfuric acid, react for 22h to 28h under stirring at 80℃ to 91℃, and finally cool to obtain a mixed product. The mixed product is placed in ice water, filtered to remove solid residues, and a filtrate is obtained. White particles are repeatedly precipitated in the filtrate to obtain a thiacalix[4]arene tetrasulfonate eluent; The mass ratio of the thiacalixarene to the concentrated sulfuric acid is 1g: (9.6-10.8)mL.

2. The use of a thiocalix[4]arene tetrasulfonate eluent according to claim 1, characterized in that The heavy metal is one of copper, zinc and lead or a mixture of several of them.

3. The use of a thiocalix[4]arene tetrasulfonate eluent according to claim 1, characterized in that In step 1, nitrogen is introduced at a rate of 0.23 g / s to 0.27 g / s to remove the generated by-product hydrogen sulfide.

4. The use of a thiocalix[4]arene tetrasulfonate eluent according to claim 1, characterized in that In step 1, the mixture is heated to 228° C. to 233° C. at a heating rate of 37° C. / min to 42° C. / min.

5. The use of a thiocalix[4]arene tetrasulfonate eluent according to claim 1, characterized in that The volume ratio of the dark red product described in step 1 to toluene is 1:(3.5-4.5); the volume ratio of the dark red product described in step 1 to ether is 1:(2.5-3.5).

6. The use of a thiocalix[4]arene tetrasulfonate eluent according to claim 1, characterized in that The concentration of the sulfuric acid solution in step 1 is 1.839 g / mL to 1.841 g / mL; the volume ratio of the dark red product in step 1 to the sulfuric acid solution is 1:(0.45 to 0.55).

7. The use of a thiocalix[4]arene tetrasulfonate eluent according to claim 1, characterized in that The drying in step 1 is specifically carried out under vacuum and at a temperature of 37° C. to 42° C. for 16 to 19 hours.

8. The use of a thiocalix[4]arene tetrasulfonate eluent according to claim 1, characterized in that The concentration of the concentrated sulfuric acid described in step 2 is 1.839 g / mL to 1.841 g / mL.

9. The use of a thiocalix[4]arene tetrasulfonate eluent according to claim 1, characterized in that The repeated precipitation of white particles from the filtrate in step 2 is specifically carried out according to the following steps: first adding NaCl to the filtrate, then adding 95% by mass ethanol, and repeating the process several times to precipitate white particles, thereby obtaining the thiocalix[4]arene tetrasulfonate eluent; the mass ratio of the volume of the filtrate to the mass of NaCl is 1 mL:(4.5-5.5) g; the volume ratio of the filtrate to the mass of 95% by mass ethanol is 1:(1.5-3.5).

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